Rechargeable batteries are widely used in many products, such as notebooks, tablets, mobile phones, and even large electric vehicles. Generally, rechargeable batteries are composed of a number of rechargeable battery cells linked in series or parallel with the same spec to fulfill a certain power supply. Although every rechargeable battery cell may have the same source, due to very small difference in materials and manufacturing among rechargeable battery cells, it leads to unbalance situation among rechargeable battery cells when they are working (charging or discharging). The unbalance situation of the rechargeable battery cells may further cause low power of the rechargeable battery cells easily, even the rechargeable battery cells would reduce their lives due to over-charge. To settle the problem of unbalance of rechargeable battery cell is an important issue during development of each rechargeable battery cell.
In order to settle the problem mentioned above, many prior arts provide balance circuit so as to dynamically balance power of two adjacent rechargeable battery cells. A commonly used method is shown in FIG. 1. A conventional balance circuit 10 for multi-battery cells is shown. The balance circuit 10 includes several battery cells (a battery cell 101, a battery cell 102 and a battery cell 103) linked in series and a controller 100. An anode of the battery cell 102 is coupled to a port 122 of the controller 100 via a resistor 112. A cathode of the battery cell 102 is coupled to a port 121 of the controller 100 via a resistor 111. In the controller 100, an internal distribution path 132 and the battery cell 102 are linked in parallel. The internal distribution path 132 is connected to an internal distribution control switch 142. A controller 100 controls the internal distribution control switch 142 via a control signal D2.
An anode of the battery cell 101 is coupled to a port 121 of the controller 100 via a resistor 111. A cathode of the battery cell 101 is coupled to a port 120 of the controller 100 via a resistor 100. In the controller 100, an internal distribution path 131 and the battery cell 101 are linked in parallel. The internal distribution path 131 is linked to an internal distribution control switch 141. The controller 100 controls the internal distribution control switch 141 via a control signal D1. An anode of the battery cell 103 is coupled to a port 123 of the controller 100 via a resistor 113. A cathode of the battery cell 103 is coupled to a port 122 of the controller 100 via a resistor 112. In the controller 100, an internal distribution path 133 and the battery cell 103 are linked in parallel. The internal distribution path 133 is linked to an internal distribution control switch 143. The controller 100 controls the internal distribution control switch 143 via a control signal D3.
When unbalance situation happens among battery cells, for example, when voltage of the battery cell 102 is higher than that of other battery cells, the controller 100 conducts the internal distribution control switch 142 so that a distribution current (not shown) flow into the internal distribution path 132 and cause charging speed of the battery cell 102 slow down. Voltages of each battery cells come to balance.
However, a defect of the method is that heat will come out in the distribution circuits and accommodate in the controller 100. It may damage the controller 100. Meanwhile, in order to balance battery cells, power in the battery cell having higher voltage us consumed. Performance of the battery is reduced.
Therefore, effective control method and power transfer circuit for transferring power between stacked rechargeable battery cells are still desired.